yes you were right. there is some misconfig in mysql parameters in postfix.

I have uninstall/reinstall ISPConfig several times. however I change the database name during the installation process, the "dbname" in files mysql-virtual_relaydomains.cf and mysql-virtual_domains.cf are remained "dbispconfig" !!!!!

Somehow your Postfix is configured for virtual users instead of system users, and this setup is incompatible with ISPConfig 2. Is it possible that you accidently used the "Perfect Server" tutorial for ISPConfig 3 instead 2?

I have removed ISPconfig and postfix rpm. then install step 12 of the perfect server manual again.

that was because the first time I had installed ISPconfig 3 and then removed it and installed ISPcnfig 2. but the configuration in /etc/postfix/mysql-virtual_* was remained.
I think the ISPconfig does not completely uninstalled by removing /root/ispconfig and /home/admispconfig !!!

I am having the same problem.
but I have not tried to uninstall / install ISPConfig because of fear of web data that already exist will also be lost (already have 2 web hosting).
Is there any solution other than the Uninstall / Install ISPConfig?

Name resolution is not working correctly on your server or you changed your mysql configuratio so that it does not listen to localhost anymore. Check your /etc/hosts file to ensure that it contains the line:

127.0.0.1 localhost

and ccheck your mysql config to ensure that mysql listens on all interfaces.

Not intend to apologize in advance for the double post, but since reading the above problem and the solution re-install ISPConfig. But because I am afraid to reinstall ISPConfignya think could be done with the upgrade version but not as well.

Then in / etc / mysql / my.cnf I add the following line "max_connections = 500" and the above error is not there anymore.
But when I try to test send email can not and appear error like my previous post.

I have tried to uninstall and install Clamav and has been updated.
I see from mailog (/ var / log / mail.log) is very much like spam email activity within 20 seconds was more than 1121 Kbytes in 204 Requests in the Mail Queue.
Is it because many of these activities that cause I can not send and receive email?
I've tried to delete the Mail Queue with the command "postsuper-d ALL" and deleted but there is always more.
Shortly after I tried to remove and test send / receive email could not be fixed.